Method of operating alternating-current motors.



V. A. FYNN. METHOD or OPERATING ALTERNATING CURRENT MOTORS. APPLICATIONFILED MAR. 29, 1912.

1 ,122,490. Patented Dec. 29, 1914.

Flgl ll 7 8 WITNESSES: lNLE/VTOR.

UNITED STATES PAENT OFFICE.

vAL'nnE ALrnnn FYNN, or s'r. LOUIS, rirssonni, nssronoa ro WAGNERELECTRIC manumoruame COMPANY, or sr. LOUIS, raissounr, A CORPORATION orMIS- SOUBI,

Specification of Letters Patent.

Patented Dec. 29, 1914.

Application filed March 29, 1912. Serial No. 687,210.

1 To all whom it may concern.

I Be it known'that I, VALhRE AL RED FYNN, 1 l a subject of the Kin ofEngland, residing i at the Buckingham otel, St. Louis, Missouri, UnitedStates of America, have invented a certain new and useful Method of()perating Alternating-Current Motors, of which the following is such afull, clear, and exact description as will enable any one skilled in theart to which it appertains to make and use the same, reference being hadto the accompanying drawings, forming part of this specification.

My invention relates to alternate current motors and is particularlyapplicable to single-phase motors used for the operation of elevatorsand the like.

One object of my invention is to enable a single-phase motor to startwith a moderate torque, but to so control the speed torque curve of themachine that the torque will never fall materially below the full loadtorque until a nearly synchronous speed is reached.

Another object is to achieve the results set forth without increasingthe flux densities of the motor above the normal, without everinterrupting the primary circuit of the motor, and, preferably, alsowithout interrupting its secondary circuit.

In the accompanying drawings, Figure 1 illustrates one embodiment of myinvention as applied to a 2-pole single phase series induction motor andFig. 2 shows a modification.

Referring to Fig. 1, 8 represents the main inducing winding of the motorand 9 the stator field Winding. The two windings are connected in seriesand across the mains 28. 29, a reversing switch 17 being interposedbetween them for the purpose of reversing the direction of the currentthrough the field Winding 9 thusreversing the direction of rotation ofthe machine. The rotor is provided with a commuted winding 16 closed byway of the brushes 11, 12 along an axis practically coinciding with thatof the main inducing winding 8. A number of points 13, 14:, 15, 20, 21,22 of said commuted winding are also adapted to be short-circuited bymeans of the conducting body 23. The brushes 11, 12 resting on thecommuted winding, or on a commutator connected thereto, are connected tothe secondary of way switch 6, one of its blades short-circuits thesecondary of the transformer 10 and the commuted winding 16 along theaxis of 8; the other blade of this two-way switch short-circuits theprimary of the trans-.

former 10. In the other position of this two-way switch, connectionbetween the leads 18 and 19 is interrupted, the shortcircuit around theprimary winding of the transformer 10 is also interrupted, and saidprimary is connected to the lead 29 at the, point 5.

The mode of operation of this improved motor is as follows: The two-wayswitch 6 being placed in the position shown in Fig. 1, switch 7 isclosed and switch 17 is thrown in the one or the other direction,according to the direction in which the motor is de sired to run. Atstarting the short-circuiting device 23 is out of contact with thepoints 13, 14c, 15, 20, 21, 22 of the commuted winding 16, and themachine starts by virtue of the interaction between the flux produced bythe stator'winding 9 and the currents induced in the'rotor winding 16 bythe stator winding 8. These currents close by way of the brushes 11, 12,partly by way of the secondary or" the transformer 10, and partly by Wayof the leads 18, 19 and one blade of the two-way switch 6. The totalnumber of turns in the stator wind- ,ings 8 and 9 are preferably sochosen as to give as low flux densities at full load as are compatiblewith the required overload capacity of the motor. Under theseconditions, the torque exerted by the motor in the starting connectionshown in Fig. 1 will be generally nearly two times the full load torqueand will, therefore, be amply suflicient to quietly start the cage of anelevator. As the speed of the motor increases, the available torque willdecrease and will finally reach a value slightly exceeding the full loadvalue at a speed greatly below the synchronous speed. This value isgenerally reached at six-tenths of the full load speed. When the torquehas decreased) to this expoints 4 and 5 that an E. M. F. derived fromthe transformer 10, the primary of which is now connected across themains, is injected into the rotor circuit comprising the brushes 11, 12.I so select'the direction and phase ofthis E. M. F. that it will assistthe E. M. F. induced in the rotor circuit by the main inducing winding8. The rotor current will thereby be increased, resulting in anincreased motor torque. It is, I find, a simple matter to so select themagnitude of this auxiliary E. M. F. that the torque produced in themotor with the help of said E. M. F. equals or slightly exceeds the fullload torque at the time when the rotor has reached a nearly synchronousspeed. 'When a speed sufficiently close to the synchronous has beenreached, I short-circuit the points 13, 14, 15, 20, 21, 22 of the rotorwinding 16, and either open the switch 7 or move the two-way switch 6back to the points 2, i

The arrangement shown in Fig. 2 differs fromthat illustrated in Fig. 1in that the auxiliary E. M. F. used for the purpose of increasing thetorque of the motor, after the rotor has reached approximately one halfof its synchronous speed, is not derived from a transformer 10 disposedoutside the motor, but is taken from the stator, in this case from themain inducing winding 8. The switch 6 is so arranged that it can, whendesired, simultaneously bridge two 'of the contacts 24, 25 or 25, 26with which it. cooperates. At starting, switch 6 is so placed as tocover contact 2 1 only and the motor is started in the one or the otherdirection by suitably throwing the reversing switch 17. After the motorhas reached a speed equal to about one half of its synchronous speed,

thefswitch 6 is moved so as to bridge con tacts 24 and 25, thus stillmaintaining the short-circuit between the brushes 11, 12 andsimultaneously closing that part of the winding 8 which is locatedbetween the points 2 1 and 30 over a resistance or inductance 27. Theswitch 6 is, however, not left in this position, but is quickly moved tothe left, thus closing the rotor winding 16 over the resistance 27 andpart of the main stator winding 8. This again is only an intermediateposition of the lever 6, which should be moved as quickly as possibleinto the position shown in Fig. 2 in which the resistance 27 is shet-circuited and the full voltage appearing bet een the points 2% and 30of the main inducing winding 8 is impressed. on the commuted winding 16.The resistance 27, together with the contact 25 are merely introduced soas to avoid a meaaeo direct short-circuit between the points 24 and 30of the main inducing winding ,8.

These points can, if necessary, be directly SllOIt-ClI'ClUlZQd, but itIS preferred to connect them by way of the resistance or inductance 27.After the motor has reached a speed suifieiently close to thesynchronous. the conducting body 23 is caused to Sh(l':x-

circuit the points 13, 1%, 15 of the commuted winding 16, and theswitch6 i s brought back to that position in which it is in contact withpoint 24 only.

11" the motor is reversed by reversing the current thiough the aux liarystator W1IlCl-. ing 9, then the direction of the auxlhary E. M. F.injected into the rotor circuit dur-- ing the latter part of its periodof acceleration must remain the same regardless of-the dlrection ofrotation of the motor. lit the motor is reversed by reversing thecurrent through the main inducing winding 8 instead of the field winding9, then this'auxiliary E. M. F. should also be reversed. For thisreason, it is generally preferred to reverse the field winding 9, asshown in the I have found that the magnitude of the auxiliary E. M. F.usually necessary in order to sufficiently raise the torque of the motorwhich the auxiliary E. M. F. is impressed on the brushes 11,12. Thiswill only result in a decrease in the efficiency of the.

motor. Since it simplifies the switching operations, this expedient maysometimes desirable one.

The invention has been described as applied to a motor, the inducingwinding of which is stationary'while the induced'memher is adapted torevolve, but it will be understood that the functions of stator and.

rotor can be readily interchanged causing the inducing member to revolvewhile keeping the induced member stationary without in the leastdeparting from the spirit of this invention.

Having fully described my invention, what I claim as new and desire tosecure by Letters Patent of the United States-is:

1. The method of operating an alternating current motor which consistsin supplying alternating current to the stator, establishing a circuitthrough the rotor win.;.- ing along an axis angularly displaced from theaxis of the resultant stator magnetization, increasing the total E. M.F. inthe rotor circuit when the rotor has reached a fraction of itssynchronous speed, and shortcircuiting the rotor winding at a pluralityof points when approximately synchronou speed has been attained.

2..The method of operating an alternating current motor which consistsin supplying alternating current to the stator, establishing a circuitthrough therotorwinding along an axis angularly displaced from the axisof the resultant stator magnetization, introducing an auxiliary E. M. F.into the rotor circuit when the rotor has reached a fraction of itssynchronous speed, and shortcircuiting the rotor winding at a pluralityof points when approximately synchronous speed has been attained.

' 3. The method of operating a single phase commutator motor whichconsists in supplying single phase current to the stator, closing thecommuted winding by way of brushes along an axis displaced from the axisof the resultant stator magnetization to start the motor, introducing anauxiliary E. M. F. into the brush circuit when the motor has attained afraction of its synchronous speed, and finally .short-circuiting thecommuted winding along a plurality of axes.

4. The method of operating a single phase commutator motor whichconsists in supplying single phase current to the stator, closing thecommuted winding by way of brushes along an axis displaced from the axisof the resultant stator magnetization to start the motor, introducing anauxiliary E. into the brush circuit when the motor has attained afraction of its synchronous speed, said E. M. F. being introducedwithout interrupting said circuit, and finally short-circuiting thecommuted winding along-a plurality of axes.

5. The method of operating a single phase commutator motor whichconsists in supplying single phase, current to the stator, closing thecommuted winding by way of brushes along an axis displaced from the axisof the resultant stator magnetization to start the motor, conductivelyintroducing an auxiliary E. M. F. into the b ush circuit when the motorhas attained a fraction of its synchronous speed, short-circuiting thecommuted winding along a plurality of axes when approximatelysynchronous speed has been reached, and finally withdrawing theauxiliary E. M. F. from the brush circuit.

6. The method of operating a single phase commutator motor whichconsists in supplying single phase current to the stator,

clos ng the commuted winding by way of brushes along an axis displacedfrom the axis of the resultant stator magnetization to start the motor,conductively introducing an auxiliary E. M. F. into the brush circuitwhen the motor has attained a fraction of its synchronous speed, said E.M. F. be ing introduced without interrupting the circuit,short-circuiting the commuted winding along a plurality of axes whenapproximately synchronous speed has been reached,

and finally VithdraWing the auxiliary E. M; F. from, the brush. circuit.

7 The method of operating a single phase commutator motor which consistsin supplying single phase current to the stator, closing the commutedwinding by way of brushes along an. axis displaced from the axis of theresultant stator magnetization to start the motor, introducing anauxiliary E. M. F. into the brush circuit when the motor has attainedapproximately one half E. M. F. approximately in phase with the line E.M. F. into the brush circuit when the motor has attained a fraction ofits synchronous speed, and finally short-circuiting the commuted windingalong a plurality of axes.

9. The method of operating a single phase commutator motor whichconsists in supplying single phase current to the stator, closing thecommuted winding by way of brushes along an axis displaced from the axisof the resultant stator magnetization to start the motor, introducing anauxiliary E. M. F. approximately in phase with the line E. M. F. intothe brush clrcuit when the motor has attained a fraction of itssynchronous speed, said E. M. F. being introduced without interruptingsaid circuit, and finally short circuiting' the commuted winding along aplurality of axes.

10. The method of operating a single phase commutator motor whichconsists in supplying single phase current to the stator, closing thecommuted winding by way of hnushes along an axis displaced from the axisof the resultant stator magnetization to start the motor, introducing anauxiliary E. M. F. derived from a stator winding into the brush circuitwhen the motor has attained a fraction of its synchronous speed, andfinally short-circuiting the commuted winding along a plurality of axes.

11. The method of operating a single phase commutator motor, whichconsists in supplying single phase current'to the stator, closing thecommutedwinding by way of brushes along an axis displaced from the axisof the resultant stator magnetization to. start the motor, conductivelyintroducing into the brush circuit an auxiliary .E. M. F.

its

derived from a stator Winding in the axis of saicl brushes When themotor has attained a fraction of its synchronous speed, andshort-cireuiting the commuted Winding along a plurality of axes whenapproximately synchronous speed has been reached.

12. The method of operating an alternating current motor in which therotor is olesecl by Way of brushes along an axis displaced from the axisof the resultant stator magnetization at starting, Which consists in lL.s-l

